Battery cell, battery device, electric device, and energy storage device

Abstract

Provided are a battery cell, a battery device, an electric device, and an energy storage device, relating to the technical field of batteries. A positive electrode sheet of the battery cell comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector; the positive electrode film layer comprises a first type of particles and a second type of particles; the first type of particles and the second type of particles each comprise a lithium-containing transition metal phosphate material; the primary particle size of the first type of particles is greater than or equal to 50 nm and less than or equal to 180 nm; the primary particle size of the second type of particles is greater than 180 nm and less than 900 nm; the average value of the Mn molar ratio of the first type of particles is less than the average value of the Mn molar ratio of the second type of particles, the Mn molar ratio referring to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. An electrolyte of the battery cell comprises a linear carboxylate solvent, and the linear carboxylate solvent comprises one or more of the structures represented by formula I.

Description

Battery cells, battery packs, electrical devices and energy storage devices Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a battery cell, battery device, power supply device, and energy storage device. Background Technology

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] With the rapid development of electric vehicles and mobile electronic devices, the requirements for the energy density and storage performance of battery cells are becoming increasingly stringent. How to maintain high energy density while simultaneously improving fast-charging and cycle performance is a pressing technical challenge in the current application of battery cells. Summary of the Invention

[0004] This application aims to at least solve one of the technical problems existing in the background art. Therefore, one object of this application is to provide a battery cell with high energy density, long cycle life, and good fast-charging performance. An embodiment of the first aspect of this application provides a battery cell including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes first-type particles and second-type particles, both of which include lithium transition metal phosphate materials. The primary particle size of the first-type particles is greater than or equal to 50 nm and less than or equal to 180 nm, and the primary particle size of the second-type particles is greater than 180 nm and less than 900 nm. The average molar percentage of Mn in the first-type particles is less than the average molar percentage of Mn in the second-type particles. The molar percentage of Mn refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. The electrolyte includes a linear carboxylic acid ester solvent, which includes one or more structures represented by Formula I.

[0005] R1 and R2 each independently include one or more of substituted or unsubstituted C1-C6 alkyl groups and C1-C6 haloalkyl groups.

[0006] The positive electrode active material comprises two types of particles with different primary particle sizes. This allows the particles of different sizes to cooperate and fill gaps, resulting in a denser particle packing and increased powder compaction density and electrode compaction density, thereby improving the battery's energy density. However, the smaller-sized first-type particles have a larger specific surface area and higher surface activity, making them more prone to side reactions with the electrolyte and exacerbating manganese ion dissolution, thus affecting the battery's cycle performance and storage performance. This application reduces the likelihood of manganese dissolution during cycling and storage by controlling the average Mn molar ratio of the smaller-sized, higher-specific-surface-area first-type particles to be lower than the average Mn molar ratio of the second-type particles. This improves the material's cycle stability and storage stability, enhancing the battery's cycle and storage performance. Simultaneously, the larger-sized, lower-specific-surface-area second-type particles have a relatively higher Mn molar ratio, which, while maintaining good cycle and storage stability, increases the plateau capacity and specific capacity of the second-type particles, contributing to higher battery energy density.

[0007] However, the large-diameter, high-Mn molar ratio of the second type of particles results in poor electron and ion transport performance, affecting the conductivity and ion diffusion performance of the cathode material, as well as the solid-phase impedance and diffusion impedance of the battery, negatively impacting its kinetic performance. Linear carboxylic acid ester solvents, on the other hand, possess polar groups such as carbonyl groups, exhibiting electrostatic adsorption. In the electrolyte, they can effectively dissociate and adsorb lithium ions from the electrolyte salt, forming freely moving ions and achieving efficient lithium ion transport. This improves the liquid-phase transport capability of the battery cell and compensates for the negative impact of the second type of particles on the battery cell's impedance. Furthermore, linear carboxylic acid ester solvents have high boiling points and low viscosity, reducing internal polarization within the battery, maintaining high lithium ion mobility in the electrolyte, and promoting the specific capacity of the cathode active material.

[0008] In summary, the embodiments of this application include a first type of particles with a primary particle size greater than or equal to 50 nm and less than or equal to 180 nm and a second type of particles with a primary particle size greater than 180 nm and less than 900 nm in the positive electrode film layer of the battery cell. The average value of the Mn molar ratio of the first type of particles with relatively high reactivity is controlled to be less than the average value of the Mn molar ratio of the second type of particles with relatively low reactivity. Furthermore, a linear carboxylic acid ester solvent as shown in Formula I is introduced into the electrolyte. This improves the electrode compaction and battery energy density while also taking into account the battery's cycle performance and fast charging performance.

[0009] In any embodiment, R1 and R2 each independently comprise one or more of substituted or unsubstituted C1-C3 alkyl groups and C1-C3 haloalkyl groups.

[0010] In any embodiment, R1 and R2 each independently include one or more of methyl, ethyl, n-propyl, isopropyl, fluoromethyl, fluoroethyl, fluoron-propyl, and fluoroisopropyl.

[0011] Linear carboxylic acid esters have the characteristic that the shorter the carbon chain, the more significant the viscosity reduction. When the linear carboxylic acid esters used in the electrolyte include the above-mentioned groups, the viscosity of the electrolyte can be further reduced, the liquid phase transport capability of lithium ions in the battery cell can be improved, and the fast charging performance of the battery cell can be further improved.

[0012] In any embodiment, the mass fraction of the linear carboxylic acid ester solvent is 10%-70%, optionally 25%-60%, based on the total mass of the electrolyte.

[0013] Lithium ions exhibit lower migration resistance in low-viscosity electrolytes, which is beneficial for improving battery fast-charging performance. However, low-viscosity electrolytes have poor lithium ion dissociation capabilities, limiting further improvements in lithium ion transport efficiency. By controlling the mass fraction of linear carboxylic acid ester solvents in the electrolyte to meet the aforementioned range, the electrolyte achieves low viscosity, high lithium ion mobility, and high lithium ion dissociation capability, effectively improving the lithium ion conductivity in the electrolyte and further enhancing battery fast-charging performance.

[0014] In any embodiment, the linear carboxylic acid ester solvent includes One or more of them.

[0015] In any embodiment, the linear carboxylic acid ester solvent includes One or more of them.

[0016] Linear carboxylic acid ester solvents have the characteristic that the shorter the carbon chain, the lower the viscosity. Including the above-mentioned linear carboxylic acid ester solvents in the electrolyte can make the electrolyte have a lower viscosity, improve the poor conductivity and high internal resistance of the positive electrode containing manganese materials, which leads to the deterioration of the dynamic performance of the battery cell, and effectively improve the migration rate of lithium ions inside the battery cell, thereby further improving the fast charging performance of the battery cell.

[0017] In any embodiment, the electrolyte further includes a cyclic carbonate solvent, which includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0018] Cyclic carbonate solvents have high dielectric constants and can effectively shield the electrostatic attraction between ions in lithium salts, accelerating the dissociation of lithium ions. The battery electrolyte of this application includes the above-mentioned cyclic carbonate solvents, which can further improve the conductivity of the electrolyte and further improve the fast charging performance of the battery.

[0019] In any embodiment, the mass fraction of the cyclic carbonate solvent is 5%-30%, optionally 20%-30%, based on the total mass of the electrolyte.

[0020] Solvents with high dielectric constants possess strong lithium-ion dissociation capabilities, which is beneficial for increasing the concentration of active lithium in the electrolyte and improving the battery's fast-charging rate performance. However, high dielectric constant solvents also have high viscosity, which is detrimental to lithium-ion migration in the electrolyte, limiting the improvement of lithium-ion transport efficiency. By controlling the mass fraction of cyclic carbonate solvents in the electrolyte to meet the aforementioned range, and through electrolyte formulation design, the electrolyte can achieve both high lithium-ion dissociation and high low viscosity and high lithium-ion mobility, effectively improving the lithium-ion conductivity in the electrolyte and further enhancing the battery's fast-charging performance.

[0021] In any embodiment, the electrolyte further includes a chain carbonate solvent, which includes one or more of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0022] In any embodiment, the mass fraction of the chain carbonate solvent is 5%-40%, optionally 20%-30%, based on the total mass of the electrolyte.

[0023] Using the aforementioned types of chain carbonate solvents in the electrolyte can be combined with cyclic carbonate solvents to balance the solvation capacity of the electrolyte, promote the dissociation of electrolyte salts, and improve the conductivity of lithium ions, thereby further improving the fast charging performance of the battery.

[0024] In any embodiment, the electrolyte further includes an additive, which includes one or more of succinic anhydride, adiponitrile, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, and vinyl sulfate. Optionally, the additive includes vinyl sulfate.

[0025] The electrolyte contains the above-mentioned additives, which can preferentially oxidize and decompose on the negative electrode surface to form a more stable and dense SEI film, reduce the damage of Mn ions dissolved from the first and / or second types of particles to the SEI film, reduce the loss of active lithium caused by rebuilding the SEI film, and thus improve the battery capacity and cycle performance.

[0026] In any embodiment, the mass fraction of the additive is 0.01%-10% based on the total mass of the electrolyte.

[0027] Excessive additive content increases film-forming resistance, leading to a higher rate of increase in the DC internal resistance of the electrolyte during cycling and a deterioration in battery kinetic performance. Controlling the mass fraction of additives in the electrolyte within the aforementioned range helps reduce the film-forming resistance of the additives. This allows the battery to maintain good storage and cycling performance while further improving the rate of increase in DC resistance during storage, thus enhancing overall battery kinetic performance.

[0028] In any embodiment, the electrolyte further includes an electrolyte salt, which includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium difluorooxalate phosphate (LiDFOP), and lithium dioxalate borate (LiBOB).

[0029] The electrolyte contains the aforementioned electrolyte salts, which can dissociate active lithium ions in the electrolyte and improve the mobility of lithium ions in the electrolyte, giving the battery high energy density, long cycle life, and excellent fast charging performance.

[0030] In any embodiment, the concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L.

[0031] Controlling the concentration of electrolyte salt to meet the above range is beneficial to improving the degree of dissociation of electrolyte salt, increasing the concentration of active lithium ions in the electrolyte, further improving lithium ion transport efficiency, and thus improving the fast charging performance of the battery.

[0032] In any embodiment, the electrolyte has a conductivity of 12 mS / cm to 16 mS / cm at room temperature.

[0033] In any embodiment, the average value of the Mn molar ratio of the first type of particles is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

[0034] Controlling the average Mn molar ratio of the first type of particles within a suitable range can reduce the possibility of side reactions between the first type of particles and the electrolyte, as well as the possibility of manganese dissolution. This can improve the cycle stability and storage stability of the first type of particles, enhance the cycle performance and storage performance of the battery, and extend the cycle life and storage life of the battery.

[0035] In any embodiment, the average Mn molar ratio of the second type of particles is 0.4-0.9, and can be optionally 0.5-0.9.

[0036] By controlling the average Mn molar ratio of the second type of particles within a suitable range, the second type of particles can have a high plateau capacity while also ensuring that the second type of particles have a certain conductivity. This is conducive to the second type of particles exerting their specific capacity, so that the second type of particles can contribute sufficient capacity, thereby improving the energy density of the battery.

[0037] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film layer, the molar percentage of Mn in the first type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

[0038] By controlling the molar percentage of Mn in the first type of particles within a suitable range, the side reactions between the small-diameter first type of particles and the electrolyte, as well as the degree of manganese dissolution, can be further reduced, thereby further improving the cycle performance and storage performance of the battery. The battery is suitable for application scenarios with high requirements for cycle performance and / or storage performance.

[0039] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is greater than 0% and less than or equal to 30%, which can be selected as 5%-20%; and / or, the area ratio of the second type of particles is greater than or equal to 70% and less than 100%, which can be selected as 80%-95%.

[0040] When the area ratio of the first type of particles and the second type of particles is within a suitable range, it can achieve particle size distribution, improve the powder compaction density and electrode compaction density of the material, and at the same time, it can give full play to the purpose of providing platform capacity for the second type of particles with relatively high manganese content. It can also reduce the impact of small-diameter first type of particles on the cycle stability and storage stability of the material, which is conducive to obtaining batteries with high energy density and excellent cycle performance and storage performance.

[0041] In any embodiment, the positive electrode film layer further includes a third type of particles, which includes lithium transition metal phosphate material. The primary particle size of the third type of particles is greater than or equal to 900 nm and less than or equal to 5 μm. Based on the total area of ​​the primary particles of the positive electrode film layer, the area ratio of the third type of particles is greater than or equal to 5%.

[0042] Compared to the first and second types of particles, the third type of particles has a larger primary particle size. During cycling or storage, these particles are less likely to undergo side reactions with the electrolyte or experience manganese dissolution. The inclusion of this third type of particle, which exhibits excellent cycle and storage stability, in the positive electrode film further improves the cycle and storage stability of the positive electrode active material, thereby enhancing the battery's cycle and storage performance. Furthermore, the presence of three types of particles with different primary particle sizes in the positive electrode film allows for a large, medium, and small particle size distribution system, resulting in a denser packing and further increasing the electrode's compaction density. Additionally, the third type of particle has a higher specific capacity, leading to a higher energy density in the battery.

[0043] In any embodiment, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

[0044] Controlling the molar percentage of Mn in the third type of particles within a suitable range can further improve the conductivity of the third type of particles, alleviate the discharge polarization of the third type of particles, and help to further improve the rate performance of the battery.

[0045] In any embodiment, the average value of the Mn molar ratio of the third type of particles is 0-0.6, optionally 0-0.5, more preferably 0-0.1, and even more preferably 0.

[0046] Controlling the average molar ratio of Mn in the third type of particles within a suitable range can improve the conductivity of the third type of particles, enhance the overall conductivity of the material, and improve the rate performance of the battery.

[0047] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 5%-15%, the area ratio of the second type of particles is 45%-85%, and / or the area ratio of the third type of particles is 10%-40%.

[0048] By controlling the area ratio of particles of different sizes within a suitable range, the contribution of the high manganese content type II particles to the energy density in terms of both the average voltage and specific capacity can be achieved. At the same time, the impact of large-diameter type III particles on the rate performance of the battery and the impact of small-diameter type I particles on the cycle performance and storage performance of the battery can be reduced. The battery can achieve a balance of high energy density, good cycle performance, storage performance and rate performance.

[0049] In any embodiment, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the second type of particles is 45%-85%, the average molar ratio of Mn in the second type of particles is 0.5-0.9, and based on the total mass of the electrolyte, the mass content of the linear carboxylic acid ester solvent is 10%-70%, and the mass content of the cyclic carbonate solvent is 5%-30%.

[0050] In any embodiment, the general formula of the lithium transition metal phosphate material of the first type of particles includes Li m1 Fe x1 Mn r1 P y1 O j1 Q1 q1 Wherein, 0.95≤m1≤1.15, x1>0, r1≥0, 0.9≤x1+r1≤1, 0.95≤y1≤1, 3.5≤j1≤4, 0≤q1≤0.1, and Q1 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br; and / or, the general formula of the lithium transition metal phosphate material of the second type of particles includes Li m2 Fe x2 Mn r2 P y2 O j2 Q2 q2 Wherein, 0.95≤m2≤1.15, x2>0, r2>0, 0.9≤x2+r2≤1, 0.95≤y2≤1, 3.5≤j2≤4, 0≤q2≤0.1, and Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0051] In any embodiment, the general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 Fe x3 Mn r3 P y3 O j3 Q3 q3 Wherein, 0.95≤m3≤1.15, x3>0, r3≥0, 0.9≤x3+r3≤1, 0.95≤y3≤1, 3.5≤j3≤4, 0≤q3≤0.1, and Q3 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0052] Selecting appropriate modifying elements Q1, Q2, and Q3 can improve the lattice change rate of the material during lithium insertion / extraction, enhance the structural stability of the material, reduce manganese dissolution, decrease oxygen activity on the particle surface, increase the energy density of the battery, and reduce interfacial side reactions between the material and the electrolyte during use, thereby improving the cycle performance and storage performance of the material.

[0053] In any embodiment, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

[0054] If the compaction density of the positive electrode sheet meets the above range, it will help to increase the specific capacity of the electrode sheet, thereby further improving the energy density of the battery.

[0055] In any embodiment, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which comprises one or more of the following: natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, lithium titanate, and lithium terephthalate.

[0056] In any embodiment, the OI value of the negative electrode film is 3-30, optionally 8-25, and further optionally 10-15.

[0057] The OI (Original Index) value of the negative electrode film reflects the orientation of the crystal structure of the negative electrode active material, representing the degree of order in the crystal structure arrangement. A lower OI value indicates a relatively higher degree of disorder in the crystal structure arrangement within the negative electrode film, which is beneficial for lithium ions to embed into the negative electrode film from various directions, improving the battery's fast-charging performance. When the OI value of the negative electrode film meets the above-mentioned range, the battery's fast-charging performance is further improved, while avoiding an increase in side reactions due to an excessively low OI value, thus ensuring a good cycle life.

[0058] In any embodiment, the porosity of the negative electrode film is 20%-60%, and optionally 35%-45%.

[0059] The porosity of the negative electrode film affects the diffusion of lithium ions within it, thus influencing the rate performance of the battery cell. Generally, higher porosity in the negative electrode film results in better electrolyte wettability and better rate performance of the battery cell. However, excessive porosity can lead to internal short circuits or high self-discharge rates. Furthermore, excessive porosity in the negative electrode active material layer is detrimental to maintaining the mechanical strength of the negative electrode film, thus worsening cycle life. When the porosity of the negative electrode film is within the aforementioned range, it is beneficial for improving the fast-charging performance of the battery cell while maintaining good cycle life.

[0060] In any embodiment, the areal density of the negative electrode film is 0.1 g / 1540.25 mm². 2 -0.2g / 1540.25mm 2 Available in 0.14g / 1540.25mm. 2 -0.19g / 1540.25mm 2 .

[0061] If the areal density of the negative electrode film meets the above range, it can effectively improve the compaction density of the negative electrode sheet, thereby effectively improving the energy density of the battery cell. However, if the areal density of the negative electrode film is too high, it will not be conducive to the migration of lithium ions into / out of the battery. In this embodiment, by adding carboxylic acid ester solvents to the electrolyte, it is beneficial to improve the migration rate of lithium ions in the electrolyte, so that the battery cell can have both high areal density and high energy density and good fast charging performance.

[0062] An embodiment of the second aspect of this application provides a battery device that includes the battery cell described in the above embodiments.

[0063] An embodiment of the third aspect of this application provides an electrical device comprising a battery cell as described in the above embodiments, the battery being used to provide electrical energy.

[0064] An embodiment of the fourth aspect of this application provides an energy storage device comprising a battery cell as described in the above embodiments, the battery being used to store electrical energy.

[0065] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0066] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0067] Figure 1 is a longitudinal cross-sectional schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0068] Figure 2 is a schematic diagram of the statistical distinction rules of primary particles in the transmission electron microscope image of particles in this application;

[0069] Figure 3 is a schematic diagram of a battery cell according to an embodiment of this application;

[0070] Figure 4 is a schematic diagram of a battery module according to an embodiment of this application;

[0071] Figure 5 is a schematic diagram of a battery pack according to an embodiment of this application;

[0072] Figure 6 is an exploded view of the battery pack shown in Figure 5;

[0073] Figure 7 is an exploded view of a battery cell according to an embodiment of this application;

[0074] Figure 8 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0075] Explanation of reference numerals in the attached drawings: 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 10 Positive electrode sheet; 110 Positive current collector; 120 Positive electrode film; 1210 Type I particles; 1220 Type II particles. Detailed Implementation

[0076] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, battery device, power consumption device, and energy storage device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0077] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0079] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0080] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0081] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0082] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0083] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0084] The cathode active material is one of the decisive factors in the performance of a battery cell. Polyanionic cathode active materials, represented by lithium iron phosphate (LFP), have advantages such as low cost, high safety, and long lifespan, which can well meet the market's requirements for high safety and low cost in battery cells. However, LFP also has some disadvantages, such as low powder compaction density and low discharge capacity, which limit its application in high-energy-density batteries. Lithium manganese iron phosphate (LFP), as a new material further developed from LFP, combines the advantages of manganese and iron, offering two voltage plateaus at 4.1V and 3.4V respectively, providing a certain plateau capacity and showing potential for high-energy-density development. However, in current research and applications, lithium manganese iron phosphate (LFP) still suffers from problems such as low compaction density and severe side reactions. The trivalent manganese ions in LFP undergo the Jan Taylor effect, transforming into tetravalent manganese ions. These highly reactive tetravalent manganese ions readily react with the electrolyte, transforming into divalent manganese ions. These divalent manganese ions further dissolve in the electrolyte, and on the one hand, they are reduced and precipitated at the negative electrode, damaging the SEI film. This causes more active lithium to be consumed during SEI film repair, thus affecting the battery's storage life. On the other hand, the presence of manganese reduces the conductivity of LFP and increases electrode impedance, thereby affecting the battery's fast-charging performance. Therefore, how to improve battery energy density while simultaneously maintaining good cycle life and fast-charging performance has become a key research focus in this field.

[0085] To address the aforementioned issues, this application provides a battery cell comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrodes. The positive electrode comprises a positive current collector and a positive electrode film layer disposed on at least one side of the current collector. The positive electrode film layer comprises a first type of particles and a second type of particles, both comprising lithium transition metal phosphate materials. The first type of particles has a primary particle size greater than or equal to 50 nm and less than or equal to 180 nm, while the second type of particles has a primary particle size greater than 180 nm and less than 900 nm. The average molar percentage of Mn in the first type of particles is less than the average molar percentage of Mn in the second type of particles. The molar percentage of Mn refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. The electrolyte comprises a linear carboxylic acid ester solvent, which includes one or more structures represented by Formula I.

[0086] R1 and R2 each independently include one or more of substituted or unsubstituted C1-C6 alkyl groups and C1-C6 haloalkyl groups.

[0087] The positive electrode active material comprises two types of particles with different primary particle sizes. This allows the particles of different sizes to cooperate and fill gaps, resulting in a denser particle packing and increased powder compaction density and electrode compaction density, thereby improving the battery's energy density. However, the smaller-sized first-type particles have a larger specific surface area and higher surface activity, making them more prone to side reactions with the electrolyte and exacerbating manganese ion dissolution, thus affecting the battery's cycle performance and storage performance. This application reduces the likelihood of manganese dissolution during cycling and storage by controlling the average Mn molar ratio of the smaller-sized, higher-specific-surface-area first-type particles to be lower than the average Mn molar ratio of the second-type particles. This improves the material's cycle stability and storage stability, enhancing the battery's cycle and storage performance. Simultaneously, the larger-sized, lower-specific-surface-area second-type particles have a relatively higher Mn molar ratio, which, while maintaining good cycle and storage stability, increases the plateau capacity and specific capacity of the second-type particles, contributing to higher battery energy density.

[0088] However, the large-diameter, high-Mn molar ratio of the second type of particles results in poor electron and ion transport performance, affecting the conductivity and ion diffusion performance of the cathode material, as well as the solid-phase impedance and diffusion impedance of the battery, negatively impacting its kinetic performance. Linear carboxylic acid ester solvents, on the other hand, possess polar groups such as carbonyl groups, exhibiting electrostatic adsorption. In the electrolyte, they can effectively dissociate and adsorb lithium ions from the electrolyte salt, forming freely moving ions and achieving efficient lithium ion transport. This improves the liquid-phase transport capability of the battery cell and compensates for the negative impact of the second type of particles on the battery cell's impedance. Furthermore, linear carboxylic acid ester solvents have high boiling points and low viscosity, reducing internal polarization within the battery, maintaining high lithium ion mobility in the electrolyte, and promoting the specific capacity of the cathode active material.

[0089] In summary, the embodiments of this application include a first type of particles with a primary particle size greater than or equal to 50 nm and less than or equal to 180 nm and a second type of particles with a primary particle size greater than 180 nm and less than 900 nm in the positive electrode film layer of the battery cell. The average value of the Mn molar ratio of the first type of particles with relatively high reactivity is controlled to be less than the average value of the Mn molar ratio of the second type of particles with relatively low reactivity. Furthermore, a linear carboxylic acid ester solvent as shown in Formula I is introduced into the electrolyte. This improves the electrode compaction and battery energy density while also taking into account the battery's cycle performance and fast charging performance.

[0090] As shown in Figure 1, the positive electrode 10 includes a positive current collector 110 and a positive electrode film 120 disposed on at least one side of the positive current collector. The positive electrode film includes first type particles 1210 and second type particles 1220.

[0091] In this paper, the term "primary particle size" refers to the particle size of a primary particle.

[0092] Lithium-containing transition metal phosphates refer to phosphate materials containing lithium and transition metal elements, and can be detected by any method known in the art. For example, they can be detected by combining X-ray diffraction (XRD) with energy dispersive spectroscopy (EDS) or inductively coupled plasma mass spectrometry (ICP-MS). As examples, lithium-containing transition metal phosphates include, but are not limited to, lithium iron phosphate, lithium manganese iron phosphate, and their doped materials.

[0093] Primary particles refer to individual particles that can be distinguished after being identified by general-purpose software (e.g., SpectrumSee; Avizo 3D) in transmission electron microscopy (TEM) images, and / or individual particles that can be distinguished after manual identification or manual-assisted calibration. Specifically, in this paper, to identify primary particles, the particles contained in the positive electrode film were enriched and / or dispersed, and then imaged under a TEM. The resulting images can be directly identified using software (based on parameters such as grayscale and / or contrast / brightness), and the individual particles that are distinguished after identification are primary particles. Alternatively, the images can be directly identified manually, and the individual particles that are distinguished after identification are primary particles. Another method is to directly identify the images using a combination of software and manual calibration, and the individual particles that are identified and confirmed to be distinguishable are primary particles. More specifically, particles that form independent, clearly distinguishable boundaries in the TEM field of view can be directly identified as individual particles through software or manual identification. However, some particles, although dispersed, exhibit a certain degree of adhesion and stacking in the TEM field of view. For particles that are stuck together or stacked, those identified as individual particles by software (based on parameters such as grayscale / contrast / brightness) are counted as first-order particles. For more precise analysis, for particles that are stuck together or stacked to some extent under a transmission electron microscope (TEM) field of view, after being identified as individual particles by software based on parameters such as grayscale / contrast / brightness, potentially misidentified particles are manually calibrated according to certain rules. The calibrated, distinguishable individual particles are then counted as first-order particles. If there are inconsistencies in the manual calibration results, 3, 5, or 7 people, unaware of each other's knowledge of the same imaging result, can individually calibrate according to the rules illustrated below. The results are then statistically calculated, and the result obtained in this way is counted as the number of first-order particles. Figure 2 is a schematic diagram of the statistical distinction rules for primary particles in a transmission electron microscope (TEM) image. Figure 2-a is the original TEM image, Figure 2-b is the software-recognized image, and Figure 2-c is an example of software and / or manual identification of independent, adhered, and stacked particles in Figure 2-a. Particles 1 and 2 are distinguishable independent particles, designated as primary particles 1 and 2, respectively. Particles 3 and 4 in Figure 2-c are adhered; particles 5, 6, and 7 are also adhered, and after software or manual identification, they are determined to be primary particles 3, 4, 5, 6, and 7, respectively. Particles 8 and 9, which are stacked together, are ultimately identified as primary particles 8 and 9, rather than being classified as a single particle. Figure 2-d is another example of software and / or manual identification of the stacked particles in Figure 2-a, where the stacked particles 10-14 are ultimately identified as primary particles 10, 11, 12, 13 and primary particle 14, instead of identifying the entire stack of particles as a single particle.When selecting the field of view for transmission electron microscopy, the field of view in which the number of stacked particles accounts for less than 20% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis. Alternatively, the field of view in which the number of stacked particles accounts for less than 15% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis. Furthermore, the field of view in which the number of stacked particles accounts for less than 10% of the total number of particles (individual particles, adherent particles, and the total number of stacked particles) can be selected for statistical analysis.

[0094] The average value of the Mn molar ratio of the first type of particles and the average value of the Mn molar ratio of the second type of particles can be tested using methods and equipment known in the art, for example as follows: Disassemble the battery to obtain the positive electrode sheet, peel off the positive electrode film layer of the positive electrode sheet, thoroughly wash the positive electrode film layer with acetone to remove the binder and dispersant in the positive electrode film layer, filter and dry to obtain powder. Take 0.05g of the uniformly mixed powder and dissolve it in 40ml of anhydrous ethanol. Then add an appropriate amount of dispersant and stir until a suspension is obtained. Take 2ml of the suspension and 2ml of anhydrous ethanol and mix them together. Then sonicate the mixture at a power of 480W for 5min. Take an appropriate amount of the middle layer suspension for transmission electron microscopy (TEM). According to the definition of primary particles mentioned above, calculate the projection area of ​​each primary particle in the TEM image, which is the cross-sectional area S of the primary particle. Use the equivalent circle method to obtain the equivalent circle diameter of the primary particle, which is the primary particle diameter d. In the above statistical process of primary particles and their primary particle diameters, primary particles with a primary particle diameter less than 50nm and greater than 5μm are not included in the statistical range (i.e., primary particles with a primary particle diameter greater than or equal to 50nm and less than or equal to 5μm are considered valid particles). Simultaneously, EDS point scanning can be used to test the molar content of Mn and Fe in each effective particle in the transmission electron microscope (TEM) image. This allows calculation of the molar percentage of Mn (X) in each effective particle (the molar percentage of Mn refers to the content of the number of moles of Mn relative to the total number of moles of Mn and Fe). The test point is the middle of the transmission surface of each particle. Multiple TEM and EDS tests are performed in different test areas, testing the cross-sectional area S, primary particle size d, and molar percentage of Mn X of at least 500 effective particles. The obtained effective particles are then numbered from smallest to largest primary particle size as 1, 2, 3, 4, 5…n, for a total of n particles. The m-th particle has a primary diameter less than or equal to 180 nm, the (m+1)-th particle has a primary diameter greater than 180 nm, the (k-1)-th particle has a primary diameter less than 900 nm, and the k-th particle has a primary diameter greater than or equal to 900 nm. Therefore, particles 1 to m are classified as Class I particles, and particles (m+1) to (k-1)-th particles are classified as Class II particles. When the primary diameter of particle n is less than 900 nm, i.e., particles 1 to m are Class I particles, and particles (m+1) to n are Class II particles, then k-1 is n.

[0095] The formula for calculating the average molar percentage of Mn in the first type of particles is as follows:

[0096] The formula for calculating the average molar percentage of Mn in the second type of particles is as follows:

[0097] Where Xi represents the molar percentage of Mn in particle i, and Si represents the cross-sectional area of ​​particle i.

[0098] In this document, the term "C1-C6 alkyl" refers to an unbranched or branched alkyl group having 1-6 carbon atoms, including but not limited to one or more of methyl, ethyl, n-propyl, 1-methylethyl (isopropyl), n-butyl, n-pentyl, and n-hexyl.

[0099] In this document, the term "C1-C6 haloalkyl" refers to an unbranched or branched alkyl group having 1-6 carbon atoms in which at least one hydrogen atom is substituted by a halogen, including but not limited to one or more of fluoroalkyl, chloroalkyl, bromoalkyl, and iodoalkyl.

[0100] Electrolyte

[0101] In some embodiments, R1 and R2 each independently comprise one or more of substituted or unsubstituted C1-C3 alkyl and C1-C3 haloalkyl groups. In some embodiments, R1 and R2 each independently comprise one or more of methyl, ethyl, n-propyl, isopropyl, fluoromethyl, fluoroethyl, fluoron-propyl, and fluoroisopropyl groups.

[0102] Linear carboxylic acid esters have the characteristic that the shorter the carbon chain, the more significant the viscosity reduction. When the linear carboxylic acid esters used in the electrolyte include the above-mentioned groups, the viscosity of the electrolyte can be further reduced, the liquid phase transport capability of lithium ions in the battery cell can be improved, and the fast charging performance of the battery cell can be further improved.

[0103] It is understood that the term "C1-C3 alkyl" represents an unbranched or branched alkyl group having 1-3 carbon atoms; the term "C1-C3 haloalkyl" represents an unbranched or branched alkyl group having 1-3 carbon atoms in which at least one hydrogen atom is substituted by a halogen.

[0104] In some embodiments, the mass fraction of the linear carboxylic acid ester solvent is 10%-70% based on the total mass of the electrolyte, and can be selected as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range between two of the above values.

[0105] In some embodiments, the mass fraction of the linear carboxylic acid ester solvent is 25%-60% based on the total mass of the electrolyte.

[0106] In this paper, the types and quantities of organic solvents and additives in the electrolyte can be determined using methods and instruments known in the art. For example, the composition of the electrolyte can be determined by liquid chromatography, ultraviolet spectrophotometry, ultraviolet-visible spectrophotometry, etc. Exemplarily, the battery cell is disassembled, and the free electrolyte is obtained from the battery cell. The free electrolyte in the battery cell is diluted 3 to 10 times with acetonitrile to obtain the diluted electrolyte solution to be tested. Using a GC-MS 3100 organic component gas chromatograph, the above diluted electrolyte solution is placed in the instrument for full-scan qualitative analysis. The injection port temperature is 250°C, and the scan range is 35 μm to 270 μm. After the test is completed, a total ion chromatogram of each organic compound is obtained. The types of organic compounds are compared according to the peak positions in the chromatogram, and the percentage content of each organic compound is calculated based on the peak area.

[0107] Lithium ions exhibit lower migration resistance in low-viscosity electrolytes, which is beneficial for improving battery fast-charging performance. However, low-viscosity electrolytes have poor lithium ion dissociation capabilities, limiting further improvements in lithium ion transport efficiency. By controlling the mass fraction of linear carboxylic acid ester solvents in the electrolyte to meet the aforementioned range, the electrolyte achieves low viscosity, high lithium ion mobility, and high lithium ion dissociation capability, effectively improving the lithium ion conductivity in the electrolyte and further enhancing battery fast-charging performance.

[0108] In some embodiments, the linear carboxylic acid ester solvent includes One or more of them.

[0109] In some embodiments, the linear carboxylic acid ester solvent includes One or more of them.

[0110] Linear carboxylic acid ester solvents have the characteristic that the shorter the carbon chain, the lower the viscosity. Including the above-mentioned linear carboxylic acid ester solvents in the electrolyte can make the electrolyte have a lower viscosity, improve the poor conductivity and high internal resistance of the positive electrode containing manganese materials, which leads to the deterioration of the dynamic performance of the battery cell, and effectively improve the migration rate of lithium ions inside the battery cell, thereby further improving the fast charging performance of the battery cell.

[0111] In some embodiments, the electrolyte further includes a cyclic carbonate solvent, which includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0112] Cyclic carbonate solvents have high dielectric constants and can effectively shield the electrostatic attraction between ions in lithium salts, accelerating the dissociation of lithium ions. The battery electrolyte of this application includes the above-mentioned cyclic carbonate solvents, which can further improve the conductivity of the electrolyte and further improve the fast charging performance of the battery.

[0113] In some embodiments, the mass fraction of the cyclic carbonate solvent is 5%-30% based on the total mass of the electrolyte, and can be selected as 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any range between any two of the above values.

[0114] In some embodiments, the mass fraction of the cyclic carbonate solvent is 20%-30% based on the total mass of the electrolyte.

[0115] Solvents with high dielectric constants possess strong lithium-ion dissociation capabilities, which is beneficial for increasing the concentration of active lithium in the electrolyte and improving the battery's fast-charging rate performance. However, high dielectric constant solvents also have high viscosity, which is detrimental to lithium-ion migration in the electrolyte, limiting the improvement of lithium-ion transport efficiency. By controlling the mass fraction of cyclic carbonate solvents in the electrolyte to meet the aforementioned range, and through electrolyte formulation design, the electrolyte can achieve both high lithium-ion dissociation and high low viscosity and high lithium-ion mobility, effectively improving the lithium-ion conductivity in the electrolyte and further enhancing the battery's fast-charging performance.

[0116] In some embodiments, the electrolyte further includes a chain carbonate solvent, which includes one or more of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

[0117] In some embodiments, the mass fraction of the chain carbonate solvent is 5%-40% based on the total mass of the electrolyte, and can be selected as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any range between two of the above values.

[0118] In some embodiments, the mass fraction of the chain carbonate solvent is 20%-30% based on the total mass of the electrolyte.

[0119] Using the aforementioned types of chain carbonate solvents in the electrolyte can be combined with cyclic carbonate solvents to balance the solvation capacity of the electrolyte, promote the dissociation of electrolyte salts, and improve the conductivity of lithium ions, thereby further improving the fast charging performance of the battery.

[0120] In some embodiments, the electrolyte further includes additives, including one or more of succinic anhydride, adiponitrile, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, and vinyl sulfate. In some embodiments, the additive includes vinyl sulfate.

[0121] The electrolyte contains the above-mentioned additives, which can preferentially oxidize and decompose on the negative electrode surface to form a more stable and dense SEI film, reduce the damage of Mn ions dissolved from the first and / or second types of particles to the SEI film, reduce the loss of active lithium caused by rebuilding the SEI film, and thus improve the battery capacity and cycle performance.

[0122] In some embodiments, the mass fraction of the additive is 0.01%-10% based on the total mass of the electrolyte, and can be selected as 0.01%, 0.05%, 0.08%, 0.10%, 0.2%, 0.5%, 0.8%, 1%, 2%, 5%, 8%, 10%, or any range between any two of the above values.

[0123] In this paper, based on the total mass of the electrolyte, the mass fraction of the additive can be tested using the test methods described above for the types and masses of organic solvents and additives in the electrolyte.

[0124] It is understandable that, due to the consumption of additives in the electrolyte during formation and cycling, and the generation of relevant components in the SEI film, the mass content of additives in the electrolyte may be slightly lower than the initial mass content of additives added to the electrolyte.

[0125] Excessive additive content increases film-forming resistance, leading to a higher rate of increase in the DC internal resistance of the electrolyte during cycling and a deterioration in battery kinetic performance. Controlling the mass fraction of additives in the electrolyte within the aforementioned range helps reduce the film-forming resistance of the additives. This allows the battery to maintain good storage and cycling performance while further improving the rate of increase in DC resistance during storage, thus enhancing overall battery kinetic performance.

[0126] In some embodiments, the electrolyte further includes an electrolyte salt, which includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium difluorooxalate phosphate (LiDFOP), and lithium dioxalate borate (LiBOB).

[0127] The electrolyte contains the aforementioned electrolyte salts, which can dissociate active lithium ions in the electrolyte and improve the mobility of lithium ions in the electrolyte, giving the battery high energy density, long cycle life, and excellent fast charging performance.

[0128] In some embodiments, the concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L, and can be selected as 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1.0 mol / L, 1.05 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, or any range between two of the above values.

[0129] Controlling the concentration of electrolyte salt to meet the above range is beneficial to improving the degree of dissociation of electrolyte salt, increasing the concentration of active lithium ions in the electrolyte, further improving lithium ion transport efficiency, and thus improving the fast charging performance of the battery.

[0130] In this paper, the type and quality of electrolyte salts can be determined using the test methods described above.

[0131] In some embodiments, the conductivity of the electrolyte at room temperature is 12 mS / cm-16 mS / cm, which can be selected as 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, or any range between any two of the above values.

[0132] In this document, the term "conductivity" describes the ability of dissociated ions in an electrolyte to conduct electricity through the directional movement of these ions in an electric field, and can be tested using any method known in the art. As an example, the following method can be used: Disassemble the battery cell, take approximately 100 mL of electrolyte sample in a dry, clean, corrosion-resistant sample bottle, seal it, and place it in a constant-temperature water bath. Shake the sample occasionally, and maintain the temperature at 25°C (deviation ±0.5°C). After the sample temperature has stabilized, use a commercially available conductivity meter to test its conductivity. After thoroughly drying the conductivity meter with calibration solution, place it vertically into the liquid to be tested, click to start the test, and record the test results after the data has stabilized for more than 10 seconds.

[0133] It is understandable that the conductivity of an electrolyte is closely related to its components and formulation, such as solvents, additives, and electrolyte salts.

[0134] When the electrolyte conductivity meets the above range, it is beneficial to improve the lithium-ion transport efficiency, enabling the battery to have high energy density while further improving the battery's fast-charging performance.

[0135] [Positive electrode active material]

[0136] In some embodiments, the average Mn molar ratio of the first type of particles is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

[0137] In some embodiments, the average value of the Mn molar ratio of the first type of particles can be selected as 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or any range between any two of the above values.

[0138] Controlling the average Mn molar ratio of the first type of particles within a suitable range can reduce the possibility of side reactions between the first type of particles and the electrolyte, as well as the possibility of manganese dissolution. This can improve the cycle stability and storage stability of the first type of particles, enhance the cycle performance and storage performance of the battery, and extend the cycle life and storage life of the battery.

[0139] In some embodiments, the average Mn molar ratio of the second type of particles is 0.4-0.9, and optionally 0.5-0.9.

[0140] In some embodiments, the average value of the molar percentage of Mn in the second type of particles can be selected as 0.4, 0.45, 0.50, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or any range between any two of the above values.

[0141] By controlling the average Mn molar ratio of the second type of particles within a suitable range, the second type of particles can have a high plateau capacity while also ensuring that the second type of particles have a certain conductivity. This is conducive to the second type of particles exerting their specific capacity, so that the second type of particles can contribute sufficient capacity, thereby improving the energy density of the battery.

[0142] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the first type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

[0143] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the first type of particles can be selected as 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or any range between any two of the above values.

[0144] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the test method for the molar percentage of Mn in the first type of particles can be performed using methods and equipment known in the art, as exemplified below: referring to the aforementioned test method for measuring the average molar percentage of Mn in the first type of particles, the cross-sectional area S and the molar percentage X of Mn for each particle are determined.

[0145] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the formula for calculating the molar percentage of Mn in the first type of particles is as follows:

[0146] Where Xi and Xj represent the molar percentage of Mn in particles numbered i and j, respectively, and Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0147] By controlling the molar percentage of Mn in the first type of particles within a suitable range, the side reactions between the small-diameter first type of particles and the electrolyte, as well as the degree of manganese dissolution, can be further reduced, thereby further improving the cycle performance and storage performance of the battery. The battery is suitable for application scenarios with high requirements for cycle performance and / or storage performance.

[0148] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles is greater than 0% and less than or equal to 30%, optionally 5%-20%; and / or, the area percentage of the second type of particles is greater than or equal to 70% and less than 100%, optionally 80%-95%.

[0149] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles can be selected as 0.5%, 1%, 2%, 5%, 7%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 27%, 30%, or any range between any two of the above values.

[0150] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the second type of particles can be selected as 80%, 81%, 82%, 85%, 87%, 90%, 92%, 95%, 98%, 99%, 99.5%, or any range between any two of the above values.

[0151] The method for testing the area ratio of the first type of particles and the area ratio of the second type of particles can be performed using methods and equipment known in the art, as exemplified below: Referring to the aforementioned method for testing the average value of the Mn molar ratio of the second type of particles, the cross-sectional area S of each particle is determined.

[0152] The formula for calculating the area ratio of the first type of particles is:

[0153] The formula for calculating the area ratio of the second type of particles is:

[0154] Where Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0155] When the area ratio of the first type of particles and the second type of particles is within a suitable range, it can achieve particle size distribution, improve the powder compaction density and electrode compaction density of the material, and at the same time, it can give full play to the purpose of providing platform capacity for the second type of particles with relatively high manganese content. It can also reduce the impact of small-diameter first type of particles on the cycle stability and storage stability of the material, which is conducive to obtaining batteries with high energy density and excellent cycle performance and storage performance.

[0156] In some embodiments, the positive electrode film layer further includes a third type of particles, which includes lithium transition metal phosphate material. The primary particle size of the third type of particles is greater than or equal to 900 nm and less than or equal to 5 μm. Based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the third type of particles is greater than or equal to 5%.

[0157] The determination of the third type of particles and the test method for their area proportion can be carried out using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for the average value of the Mn molar proportion of the first type of particles, the kth to nth particles are defined as the third type of particles. The formula for calculating the area proportion of the third type of particles is:

[0158] Where Xi represents the molar percentage of Mn in particle i, and Si represents the cross-sectional area of ​​particle i.

[0159] Compared to the first and second types of particles, the third type of particles has a larger primary particle size. During cycling or storage, these particles are less likely to undergo side reactions with the electrolyte or experience manganese dissolution. The inclusion of this third type of particle, which exhibits excellent cycle and storage stability, in the positive electrode film further improves the cycle and storage stability of the positive electrode active material, thereby enhancing the battery's cycle and storage performance. Furthermore, the presence of three types of particles with different primary particle sizes in the positive electrode film allows for a large, medium, and small particle size distribution system, resulting in a denser packing and further increasing the electrode's compaction density. Additionally, the third type of particle has a higher specific capacity, leading to a higher energy density in the battery.

[0160] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

[0161] In some embodiments, based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%. %, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or a range between any two of the above values.

[0162] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the test method for the molar percentage of Mn in the third type of particles can be performed using methods and equipment known in the art, as exemplified below: Referring to the aforementioned test method for determining the average molar percentage of Mn in the third type of particles, the cross-sectional area S and the molar percentage X of Mn for each particle are determined.

[0163] Based on the total number of moles of Mn in the primary particles of the positive electrode film, the formula for calculating the molar percentage of Mn in the third type of particles is as follows:

[0164] Where Xi and Xj represent the molar percentage of Mn in particles numbered i and j, respectively, and Si and Sj represent the cross-sectional areas of particles numbered i and j, respectively.

[0165] Controlling the molar percentage of Mn in the third type of particles within a suitable range can further improve the conductivity of the third type of particles, alleviate the discharge polarization of the third type of particles, and help to further improve the rate performance of the battery.

[0166] In some embodiments, the average Mn molar percentage of the third type of particles is 0-0.6, optionally 0-0.5, more preferably 0-0.1, and even more preferably 0.

[0167] In some embodiments, the average value of the Mn molar percentage of the third type of particles can be selected as 0, 0.0001, 0.0002, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.6, or any range between any two of the above values.

[0168] Controlling the average molar ratio of Mn in the third type of particles within a suitable range can improve the conductivity of the third type of particles, enhance the overall conductivity of the material, and improve the rate performance of the battery.

[0169] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 5%-15%, the area ratio of the second type of particles is 45%-85%, and / or the area ratio of the third type of particles is 10%-40%.

[0170] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any two of the above values.

[0171] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the second type of particles is 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or a range between any two of the above values.

[0172] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the third type of particles is 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or any range between any two of the above values.

[0173] By controlling the area ratio of particles of different sizes within a suitable range, the contribution of the high manganese content type II particles to the energy density in terms of both the average voltage and specific capacity can be achieved. At the same time, the impact of large-diameter type III particles on the rate performance of the battery and the impact of small-diameter type I particles on the cycle performance and storage performance of the battery can be reduced. The battery can achieve a balance of high energy density, good cycle performance, storage performance and rate performance.

[0174] In some embodiments, based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the second type of particles is 45%-85%, the average molar ratio of Mn in the second type of particles is 0.5-0.9, and based on the total mass of the electrolyte, the mass content of the linear carboxylic acid ester solvent is 10%-70%, and the mass content of the cyclic carbonate solvent is 5%-30%.

[0175] In some embodiments, the general formula of the lithium transition metal phosphate material of the first type of particles includes Li m1 Fe x1 Mn r1 P y1 O j1 Q1 q1Wherein, 0.95≤m1≤1.15, x1>0, r1≥0, 0.9≤x1+r1≤1, 0.95≤y1≤1, 3.5≤j1≤4, 0≤q1≤0.1, and Q1 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0176] In some embodiments, the general formula of the lithium transition metal phosphate material of the second type of particles includes Li m2 Fe x2 Mn r2 P y2 O j2 Q2 q2 Wherein, 0.95≤m2≤1.15, x2>0, r2>0, 0.9≤x2+r2≤1, 0.95≤y2≤1, 3.5≤j2≤4, 0≤q2≤0.1, and Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0177] In some embodiments, the general formula of the lithium-containing transition metal phosphate material of the third type of particles includes Li m3 Fe x3 Mn r3 P y3 O j3 Q3 q3 Wherein, 0.95≤m3≤1.15, x3>0, r3≥0, 0.9≤x3+r3≤1, 0.95≤y3≤1, 3.5≤j3≤4, 0≤q3≤0.1, and Q3 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

[0178] In some embodiments, m1, m2, and m3 can each independently be 0.95, 0.98, 1.00, 1.03, 1.05, 1.08, 1.10, 1.13, 1.15, or a range between any two of the above values. In some embodiments, x1+r1, x2+r2, and x3+r3 can each independently be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or a range between any two of the above values. In some embodiments, y1, y2, or y3 can each independently be 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, or a range between any two of the above values. In some implementations, j1, j2, and j3 can each independently be 3.5, 3.6, 3.7, 3.8, 3.9, 4, or a range between any two of the above values. In some implementations, q1, q2, and q3 can each independently be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or a range between any two of the above values.

[0179] Selecting appropriate modifying elements Q1, Q2, and Q3 can improve the lattice change rate of the material during lithium insertion / extraction, enhance the structural stability of the material, reduce manganese dissolution, decrease oxygen activity on the particle surface, increase the energy density of the battery, and reduce interfacial side reactions between the material and the electrolyte during use, thereby improving the cycle performance and storage performance of the material.

[0180] In this paper, the modifying elements Q1, Q2, and Q3 can exist in the lithium-containing transition metal phosphate material as doping elements, or in the coating layer of the material as coating elements.

[0181] [Positive electrode plate]

[0182] In some implementations, as an example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0183] In some embodiments, the compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 2.25g / cm³ is an optional value. 3 2.30g / cm 3 2.35g / cm 3 2.40 g / cm 3 2.45g / cm 3 2.50g / cm 3 2.55g / cm3 2.60g / cm 3 2.65g / cm 3 2.70 g / cm 3 2.75g / cm 3 , or the range between any two of the above values.

[0184] In this paper, the compaction density of the positive electrode sheet can be tested using methods and equipment known in the art. As an example, it can be determined as follows: a test sample of electrode sheet with area S is weighed using an electronic balance, the weight is recorded as W, and the thickness T of the electrode sheet is measured using a micrometer. Then, the compaction density = W / (T×S). The thickness of the positive electrode film layer can be measured using a micrometer (e.g., a Mitutoyo 293-100 model with an accuracy of 0.1 μm).

[0185] If the compaction density of the positive electrode sheet meets the above range, it will help to increase the specific capacity of the electrode sheet, thereby further improving the energy density of the battery.

[0186] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, conductive polymers, metal powders, and carbon nanofibers.

[0187] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0188] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. An example of a metal material may be at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymer substrate may be at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0189] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0190] [Negative electrode plate]

[0191] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0192] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0193] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which comprises one or more of the following: natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, lithium titanate, and lithium terephthalate.

[0194] In some embodiments, the OI value of the negative electrode film is 3-30, and can be selected from 3, 5, 8, 10, 12, 15, 18, 20, 22, 24, 25, 26, 28, 30, or any range between two of the above values. In some embodiments, the OI value of the negative electrode film is 8-25. In some embodiments, the OI value of the negative electrode film is 10-15.

[0195] In this paper, the term "OI value" refers to the degree of order in the arrangement of crystals or particles in a material, which can be determined using an orientation analyzer or an X-ray diffractometer. An example is shown below: Using an X-ray diffractometer (such as a Bruker D8 Discover), the test can be performed according to JISK0131-1996 and JB / T 4220-2011. The X-ray diffraction pattern of the material is obtained, and the OI value is calculated using the formula OI value = I004 / I110. I004 is the integrated area of ​​the diffraction peak of the 004 crystal plane of crystalline carbon in the material, and I110 is the integrated area of ​​the diffraction peak of the 110 crystal plane of crystalline carbon in the material. In the X-ray diffraction analysis test of this application, a copper target can be used as the anode target, and CuKα rays can be used as the radiation source. The wavelength of the rays is... The scanning 2θ angle range is 20°-80°, and the scanning rate is 4° / min.

[0196] The OI value of the negative electrode film can be controlled by adjusting the OI value of the negative electrode active material, or by controlling the manufacturing process of the electrode sheet, such as the rolling pressure.

[0197] The OI (Original Index) value of the negative electrode film reflects the orientation of the crystal structure of the negative electrode active material, representing the degree of order in the crystal structure arrangement. A lower OI value indicates a relatively higher degree of disorder in the crystal structure arrangement within the negative electrode film, which is beneficial for lithium ions to embed into the negative electrode film from various directions, improving the battery's fast-charging performance. When the OI value of the negative electrode film meets the above-mentioned range, the battery's fast-charging performance is further improved, while avoiding an increase in side reactions due to an excessively low OI value, thus ensuring a good cycle life.

[0198] In some embodiments, the porosity of the negative electrode film layer is 20%-60%, optionally selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any range between two of the above values. In some embodiments, the porosity of the negative electrode film layer is 35%-45%.

[0199] In this paper, the porosity of the negative electrode film can be tested using methods and equipment known in the art. As an example, the following method can be used for determination: Take a negative electrode sheet coated on one side and cold-pressed (if it is a double-sided coated negative electrode sheet, the negative electrode film layer on one side can be wiped off first), and cut it into small circular samples with a diameter of 14 mm; test the thickness of the negative electrode film (thickness of the negative electrode sheet - thickness of the negative current collector); calculate the apparent volume V1 of the negative electrode film according to the cylindrical volume calculation formula; using an inactive gas such as helium or nitrogen as a medium, employ the gas displacement method and a true density meter (e.g., Micromeritics AccuPyc II 1340) to measure the true volume of the negative electrode sheet, referring to GB / T 24586 2009; subtract the volume of the negative current collector from the true volume of the negative electrode sheet to obtain the true volume V2 of the negative electrode film; the porosity of the negative electrode film = (V1-V2) / V1×100%. Multiple electrode samples (e.g., 30) can be tested, and the average value of the results can be taken to improve the accuracy of the test results.

[0200] The parameters of the cold pressing process of the negative electrode sheet, such as the cold pressing speed, cold pressing temperature, cold pressing pressure, and number of cold pressing cycles, also affect the degree of compact packing of the negative electrode active material particles in the negative electrode film, and thus affect the porosity of the negative electrode film layer. Therefore, the porosity of the negative electrode film layer can be adjusted by controlling the parameters of the cold pressing process of the negative electrode sheet.

[0201] The porosity of the negative electrode film affects the diffusion of lithium ions within it, thus influencing the rate performance of the battery cell. Generally, higher porosity in the negative electrode film results in better electrolyte wettability and better rate performance of the battery cell. However, excessive porosity can lead to internal short circuits or high self-discharge rates. Furthermore, excessive porosity in the negative electrode active material layer is detrimental to maintaining the mechanical strength of the negative electrode film, thus worsening cycle life. When the porosity of the negative electrode film is within the aforementioned range, it is beneficial for improving the fast-charging performance of the battery cell while maintaining good cycle life.

[0202] In some embodiments, the areal density of the negative electrode film is 0.1 g / 1540.25 mm². 2 -0.2g / 1540.25mm 2 Available in 0.1g / 1540.25mm. 2 0.11g / 1540.25mm 2 0.12g / 1540.25mm 2 0.13g / 1540.25mm 2 0.14g / 1540.25mm 2 0.15g / 1540.25mm 2 0.16g / 1540.25mm 2 0.17g / 1540.25mm 2 0.18g / 1540.25mm 2 0.19g / 1540.25mm 2 0.2g / 1540.25mm 2 In some embodiments, the coating mass of the negative electrode film is 0.14 g / 1540.25 mm. 2 -0.19g / 1540.25mm 2 .

[0203] In this paper, the areal density of the negative electrode film can be tested using methods or instruments known in the art. As an example, the following method can be used: a negative electrode sheet with a single-sided coating is prepared to have an area of ​​1540.25 mm². 2 Take 20 small round pieces and weigh them. The coating mass = (mass of small round pieces - mass of current collector). The average value of the test is the areal density of the film layer in the example or comparative example.

[0204] If the areal density of the negative electrode film meets the above range, it can effectively improve the compaction density of the negative electrode sheet, thereby effectively improving the energy density of the battery cell. However, if the areal density of the negative electrode film is too high, it will not be conducive to the migration of lithium ions into / out of the battery. In this embodiment, by adding carboxylic acid ester solvents to the electrolyte, it is beneficial to improve the migration rate of lithium ions in the electrolyte, so that the battery cell can have both high areal density and high energy density and good fast charging performance.

[0205] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0206] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0207] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0208] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0209] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0210] [Battery cell]

[0211] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0212] A battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. A battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited to this. Figure 3 shows a cuboid battery cell 5 as an example.

[0213] A single battery cell includes electrode components and an electrolyte.

[0214] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0215] In some embodiments, as shown in FIG4, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted as needed.

[0216] Electrode assemblies typically include positive and negative electrodes. The negative electrode is the electrode that absorbs or lithiates lithium ions during charging and releases or delithiates lithium during discharging. The positive electrode is the electrode that absorbs or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0217] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0218] In some implementations, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0219] In some implementations, individual battery cells can be assembled into a battery module. The number of battery cells in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 5 is a schematic diagram of a battery module 4 as an example. As shown in Figure 5, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0220] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0221] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0222] Figures 6 and 7 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 6 and 7, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0223] [Electrical appliances]

[0224] In addition, this application also provides an electrical device that uses a battery as a power source, the electrical device including at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0225] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0226] Figure 8 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the individual battery cells, a battery pack or battery module can be used.

[0227] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0228] This application also provides an energy storage device that uses a battery as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0229] Example

[0230] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0231] Table 1. Relevant parameters and sources of lithium-containing transition metal phosphate materials.

[0232] Example 1

[0233] 1. Preparation of battery cells

[0234] (1) Preparation of positive electrode sheet

[0235] The lithium transition metal phosphate materials shown in Table 1 A1 and B1 are mixed at a mass ratio of 15%:85% to obtain the positive electrode active material. The above-mentioned mixed positive electrode active material, conductive carbon black, and binder polyvinylidene fluoride are mixed at a weight percentage of 96:1.5:2.5 and N-methylpyrrolidone is added. After thorough mixing, stirring, and dispersion, a positive electrode slurry is prepared.

[0236] The viscosity of the thoroughly mixed slurry was adjusted to 8000 mPa·s-20000 mPa·s until it did not separate into layers. The slurry was then coated onto the surface of the current collector aluminum foil using a double-sided, double-control coating device. After drying, cold pressing, slitting, and sheet forming, the positive electrode sheet was finally obtained.

[0237] (2) Preparation of negative electrode sheet

[0238] Artificial graphite, conductive carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed evenly in a weight percentage of 96.5:0.5:1.0:1.0. Deionized water was added, and the mixture was stirred and dispersed to obtain a negative electrode slurry. The negative electrode slurry was coated onto a copper foil substrate, and after drying, cold pressing, slitting, and sheet forming, a negative electrode sheet with an areal density of 180 mg / 1540.25 mm² was obtained. 2 .

[0239] (3) Separating membrane

[0240] Polypropylene film is used as the separator.

[0241] (4) Electrolyte

[0242] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethyl acetate (EA), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed evenly in a mass ratio of 50:25:25, and then ethylene sulfate DTD was added as an additive. After mixing evenly, LiPF6 (electrolyte salt) was added and dissolved in an organic solvent to make the electrolyte concentration 1 mol / L and the DTD mass content 1%. The mixture was stirred evenly to obtain the electrolyte of Example 1.

[0243] (5) Preparation of battery cells

[0244] The positive electrode, separator, and negative electrode are stacked in sequence. The separator must be able to isolate the positive and negative electrodes. The bare cell is obtained by winding. The bare cell is placed in the outer packaging, electrolyte is injected, and it goes through processes such as encapsulation, formation, and venting to finally obtain a battery cell.

[0245] The porosity of the negative electrode film in the negative electrode sheet is 35%; the OI value of the negative electrode film is 15.

[0246] Examples 2-4

[0247] The preparation methods of the battery cells in Examples 2-4 are similar to those in Example 1, except that the type of linear carboxylic acid ester solvent in the electrolyte is changed. The specific parameters are shown in Table 2.

[0248] Examples 5-9

[0249] The preparation methods of the battery cells in Examples 5-9 are similar to those in Example 1, except that the mass content of linear carboxylic acid ester solvents, chain carbonate solvents, cyclic carbonate solvents, and additives in the electrolyte is changed. Specific parameters are shown in Table 2.

[0250] Examples 10-12

[0251] The preparation methods of the battery cells in Examples 10-12 are similar to those in Example 1. The difference is that the OI value of the negative electrode film is adjusted by selecting graphite as the negative electrode active material with different OI values; and the porosity of the negative electrode film in the negative electrode sheet is adjusted by adjusting the cold pressing pressure and the number of cold pressing cycles. Specific parameters are shown in Table 2.

[0252] Examples 13-17

[0253] The preparation methods for the battery cells in Examples 13-17 are similar to those in Example 1, except that the preparation method for the positive electrode sheet is changed:

[0254] In Example 13, the positive electrode active material was prepared by mixing lithium transition metal phosphate materials as shown in Table 1 (A3 and B1) at a mass ratio of 15% to 85%.

[0255] In Example 14, the positive electrode active material was prepared by mixing lithium transition metal phosphate materials as shown in Table 1 A2 and B2 at a mass ratio of 15%:85%.

[0256] In Example 15, the positive electrode active material was prepared by mixing lithium transition metal phosphate materials as shown in Table 1 A1 and B1 at a mass ratio of 10%:90%.

[0257] In Example 16, the positive electrode active material was prepared by mixing lithium transition metal phosphate materials as shown in Table 1 (A1, B1, C1) in a mass ratio of 5%:75%:20%.

[0258] In Example 17, the positive electrode active material was prepared by mixing lithium transition metal phosphate materials as shown in Table 1 (A1, B1, C2) in a mass ratio of 10%:30%:60%.

[0259] Comparative Example 1

[0260] The preparation method of the battery cell in Comparative Example 1 is similar to that in Example 1, except that no linear carboxylic acid ester solvent is added to the electrolyte. Specific parameters are shown in Table 2.

[0261] Comparative Example 2

[0262] The preparation method of the battery cell in Comparative Example 2 is similar to that in Example 1. The difference is that the preparation method of the positive electrode sheet is changed. The positive electrode sheet is a positive active material made by mixing lithium transition metal phosphate materials shown in A4 and B1 at a mass ratio of 15%:85%.

[0263] Table 2

[0264] 2. Performance Characterization and Testing Methods

[0265] (1) Battery cell fast charging time test method

[0266] ① Voltage calibration: The prepared battery cells were charged at 0.33C at 25℃ to the charging cutoff voltage of 4.15V, and then constant voltage charging was continued at the charging cutoff voltage until the current was 0.05C, at which point charging was cut off (where C represents the rated capacity of the battery cell); the cells were left to stand at 25℃ for 1 hour; the battery cells were then discharged at 0.33C at 25℃ to the discharge cutoff voltage of 2.0V, and the total discharge capacity C0 of the battery cells was recorded; the cells were left to stand at 25℃ for 1 hour.

[0267] ② Room temperature charging test: Discharge the battery cell at 0.33C0 DC to the discharge cutoff voltage of 2.0V, corresponding to 0% SOC; let it rest for 5 minutes; charge at 5C0 constant current to the negative electrode potential of 0V, and read the capacity C1 at this point, corresponding to C1 / C0 SOC; let it rest for 5 minutes; charge at 4.5C0 constant current to the negative electrode potential of 0V, and read the capacity C2 at this point, corresponding to C2 / C0 SOC; let it rest for 5 minutes; charge at 4C0 constant current to the negative electrode potential of 0V, and read the capacity C3 at this point, corresponding to C3 / C0 SOC; let it rest for 5 minutes; charge at 3C0 constant current to the negative electrode potential of 0V, and read the capacity C4 at this point, corresponding to C4 / C0 SOC; let it rest for 5 minutes. 1. Charge with 2C0 constant current until the negative electrode potential reaches 0V, read the capacity C5 at this point, corresponding to C5 / C0SOC; let rest for 5 minutes; 2. Charge with 1C0 constant current until the negative electrode potential reaches 0V, read the capacity C6 at this point, corresponding to C6 / C0SOC; let rest for 5 minutes; 3. Charge with 0.8C0 constant current until the negative electrode potential reaches 0V, read the capacity C7 at this point, corresponding to C7 / C0SOC; let rest for 5 minutes; 4. Charge with 0.5C0 constant current until the negative electrode potential reaches 0V, read the capacity C8 at this point, corresponding to C8 / C0SOC; let rest for 5 minutes; 5. Charge with 0.33C0 constant current until the negative electrode potential reaches 0V, read the capacity C9 (also known as C0), corresponding to 100%SOC. The required charging time is obtained by summing the total charging time from 10%SOC to 80%SOC.

[0268] (2) Battery cell cycle life test method

[0269] At 25°C, charge the battery to 4.15V at a charging rate of 0.5C (the nominal capacity), then charge it to 0.05C at a constant voltage of 4.15V, let it stand for 10 minutes, and then discharge it to 2.0V at a discharging rate of 1C, let it stand for 10 minutes. One charge-discharge cycle is one cycle. Continue the test until the battery capacity decays to 90% of the nominal capacity. This number of cycles is recorded as the number of cycles @ 90% SOH.

[0270] (3) Battery cell energy density testing method

[0271] Battery cell capacity test: The battery cell was left to stand at 40℃ for 2 hours to ensure the temperature of the battery cell was 40℃. Then the battery was discharged at a constant current of 1 / 3C to 2.0V. After standing for 5 minutes, the battery cell was charged at a constant current of 1 / 3C to 4.1V. The constant voltage charging at 4.1V continued until the current was 0.05C. After standing for 5 minutes, the battery cell was discharged at a constant current of 1 / 3 to 2.0V. The total discharge capacity C0 and the total discharge energy E0 of the battery cell were recorded. The unit of total discharge energy is Wh.

[0272] Battery cell volume measurement: Use calipers to measure the length, width, and height of the battery's outer surface, and calculate the cell volume V0 in liters (L).

[0273] Volumetric energy density calculation: The volumetric energy density of a battery cell is calculated as follows: Discharge energy of a single battery cell E0 / Battery volume V0.

[0274] 3. Analysis of test results for each embodiment and comparative example

[0275] Battery cells for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Tables 3-5 below.

[0276] Table 3

[0277] The positive electrode film layer in Embodiments 1-14 of this application includes a first type of particles and a second type of particles, wherein the primary particle size of the first type of particles is greater than or equal to 50 nm and less than or equal to 180 nm, the primary particle size of the second type of particles is greater than 180 nm and less than 900 nm, and the average value of the Mn molar ratio of the first type of particles is less than the average value of the Mn molar ratio of the second type of particles.

[0278] Table 4

[0279] The positive electrode film layer in embodiments 15-17 of this application further includes a third type of particles, wherein the primary particle size of the third type of particles is greater than or equal to 900 nm and less than or equal to 5 μm.

[0280] Table 5

[0281] As can be seen from the comparison of Examples 1-17 and Comparative Examples 1-2 in Tables 3-5, the positive electrode film of the battery cell contains first-type particles with a primary particle size of ≥50nm and ≤180nm and second-type particles with a primary particle size of ≥180nm and ≤900nm. Furthermore, the average molar ratio of Mn in the first-type particles with relatively high reactivity is less than the average molar ratio of Mn in the second-type particles with relatively low reactivity. This can effectively improve the specific capacity of the positive electrode active material, which is beneficial to improving the battery energy density, while also improving the cycle and storage stability of the material. In addition, the introduction of linear carboxylic acid ester solvents as shown in Formula I into the electrolyte can improve the battery energy density while taking into account the battery's cycle performance and fast charging performance.

[0282] As can be seen from the comparison between Comparative Example 1 and Example 9 in Table 5, when the electrolyte in the battery cell does not contain linear carboxylic acid ester solvents, although the battery has a good cycle life, its fast charging performance is poor, which is not conducive to improving the overall performance of the battery cell. However, when ethyl acetate, a linear carboxylic acid ester solvent, is added to the electrolyte, the electrolyte has good conductivity, which can improve the lithium ion transport efficiency and improve the battery's fast charging performance while improving the battery's energy density.

[0283] As can be seen from the comparison of Examples 5-9 in Table 5, based on the total mass of the electrolyte, when the mass fraction of the linear carboxylic acid ester solvent is 10%-70%, and can be selected as 25%-60%, the conductivity of lithium ions in the electrolyte can be effectively improved through electrolyte formulation design, thereby further improving the fast charging performance of the battery.

[0284] As can be seen from the comparison between Examples 1 and 9 in Table 5, the electrolyte in the battery cell also includes additives. Further, the additives include ethylene sulfate. Based on the total mass of the electrolyte, when the mass fraction of the additives is 0.01%-10%, it is beneficial to form a stable SEI film on the negative electrode surface, reduce lithium consumption, and further improve the battery capacity and cycle performance.

[0285] As can be seen from the comparison of Examples 1-4 in Table 5, the addition of linear carboxylic acid esters, including ethyl acetate, methyl acetate, ethyl difluoroacetate, and methyl difluoroacetate, to the electrolyte of the battery cell can effectively improve the mobility of lithium ions, thereby further improving the fast charging performance of the battery.

[0286] As can be seen from the comparison of Examples 1 and 10-12 in Table 5, when the OI value of the negative electrode film in the battery cell is 3-30, and can be selected as 10-15, and the porosity of the negative electrode film is 20%-60%, and can be selected as 35%-45%, it is beneficial to improve the fast charging performance of the battery cell while maintaining good cycle life.

[0287] As can be seen from the comparison of Examples 1, 13, 14 and Comparative Example 2 in Tables 3-5, the average molar percentage of Mn in the first type of particles with small particle size and high specific surface area is less than the average molar percentage of Mn in the second type of particles. This can reduce the possibility of manganese dissolution in the highly reactive first type of particles during cycling and storage, improve the cycle stability and storage stability of the material, and enhance the cycle performance of the battery. As can be seen from the comparison of Examples 15, 16, and 17, the positive electrode film contains first type particles, second type particles, and third type particles, with the area ratio of first type particles being 5%-15%, the area ratio of second type particles being 45%-85%, and the area ratio of third type particles being 10%-40%. The battery has a long cycle life, short charging time, and high energy density, taking into account the cycle performance, rate performance, and energy density of the battery.

[0288] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, It includes a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a first type of particles and a second type of particles, wherein the first type of particles and the second type of particles include lithium transition metal phosphate materials. Wherein, the primary particle size of the first type of particles is greater than or equal to 50 nm and less than or equal to 180 nm, and the primary particle size of the second type of particles is greater than 180 nm and less than 900 nm. The average value of the Mn molar percentage of the first type of particles is less than the average value of the Mn molar percentage of the second type of particles, wherein the Mn molar percentage refers to the ratio of the number of moles of Mn to the total number of moles of Mn and Fe. The electrolyte comprises a linear carboxylic acid ester solvent, which includes one or more of the structures shown in Formula I: R1 and R2 each independently include one or more of C1-C6 alkyl groups and C1-C6 haloalkyl groups.

2. The battery cell according to claim 1, characterized in that, R1 and R2 each independently include one or more of C1-C3 alkyl groups and C1-C3 haloalkyl groups.

3. The battery cell according to claim 1 or 2, characterized in that, R1 and R2 each independently include one or more of the following: methyl, ethyl, n-propyl, isopropyl, fluoromethyl, fluoroethyl, fluoron-propyl, and fluoroisopropyl.

4. The battery cell according to any one of claims 1 to 3, characterized in that, Based on the total mass of the electrolyte, the mass fraction of the linear carboxylic acid ester solvent is 10%-70%, optionally 25%-60%.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The linear carboxylic acid ester solvents include One or more of them.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The linear carboxylic acid ester solvents include One or more of them.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The electrolyte also includes cyclic carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

8. The battery cell according to claim 7, characterized in that, Based on the total mass of the electrolyte, the mass fraction of the cyclic carbonate solvent is 5%-30%, optionally 20%-30%.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The electrolyte also includes chain carbonate solvents, which include one or more of methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.

10. The battery cell according to claim 9, characterized in that, Based on the total mass of the electrolyte, the mass fraction of the chain carbonate solvent is 5%-40%, optionally 20%-30%.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The electrolyte also includes additives, which include one or more of succinic anhydride, adiponitrile, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, and vinyl sulfate. Optionally, the additives include vinyl sulfate.

12. The battery cell according to claim 11, characterized in that, Based on the total mass of the electrolyte, the mass fraction of the additive is 0.01-10%.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The electrolyte further includes an electrolyte salt, which includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium difluorooxalate phosphate (LiDFOP), and lithium dioxalate borate (LiBOB).

14. The battery cell according to claim 13, characterized in that, The concentration of the electrolyte salt is 0.8 mol / L to 1.2 mol / L.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The electrolyte has a conductivity of 12 mS / cm to 16 mS / cm at room temperature.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The average molar ratio of Mn in the first type of particles is 0-0.6, optionally 0-0.4, more preferably 0-0.2, and even more preferably 0.

17. The battery cell according to any one of claims 1 to 16, characterized in that, The average molar ratio of Mn in the second type of particles is 0.4-0.9, and can be selected as 0.5-0.

9.

18. The battery cell according to any one of claims 1 to 17, characterized in that, Based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the first type of particles is 0%-12%, optionally 0%-8%, more preferably 0%-6%, and even more preferably 0%.

19. The battery cell according to any one of claims 1 to 18, characterized in that, Based on the total area of ​​the primary particles in the positive electrode film, the area percentage of the first type of particles is greater than 0% and less than or equal to 30%, which can be selected as 5%-20%; and / or, the area percentage of the second type of particles is greater than or equal to 70% and less than 100%, which can be selected as 80%-95%.

20. The battery cell according to any one of claims 1 to 19, characterized in that, The positive electrode film layer also includes a third type of particles, which includes lithium transition metal phosphate materials. The primary particle size of the third type of particles is greater than or equal to 900 nm and less than or equal to 5 μm. Based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the third type of particles is greater than or equal to 5%.

21. The battery cell according to claim 20, characterized in that, Based on the total number of moles of Mn in the primary particles of the positive electrode film, the molar percentage of Mn in the third type of particles is 0%-50%, optionally 0%-30%, more preferably 0%-10%, and even more preferably 0%.

22. The battery cell according to claim 20 or 21, characterized in that, The average molar percentage of Mn in the third type of particles is 0-0.6, which can be selected as 0-0.5, more preferably 0-0.1, and even more preferably 0.

23. The battery cell according to any one of claims 20 to 22, characterized in that, Based on the total area of ​​the primary particles in the positive electrode film layer, the area ratio of the first type of particles is 5%-15%. The area ratio of the second type of particles is 45%-85%, and / or, The area ratio of the third type of particles is 10%-40%.

24. The battery cell according to any one of claims 1 to 23, characterized in that, Based on the total area of ​​the primary particles in the positive electrode film, the area ratio of the second type of particles is 45%-85%, the average molar ratio of Mn in the second type of particles is 0.5-0.9, and based on the total mass of the electrolyte, the mass content of the linear carboxylic acid ester solvent is 10%-70%, and the mass content of the cyclic carbonate solvent is 5%-30%.

25. The battery cell according to any one of claims 1 to 24, characterized in that, The general formula of the lithium-containing transition metal phosphate material of the first type of particles includes Li m1 Fe x1 Mn r1 P y1 O j1 Q1 q1 Wherein, 0.95≤m1≤1.15, x1>0, r1≥0, 0.9≤x1+r1≤1, 0.95≤y1≤1, 3.5≤j1≤4, 0≤q1≤0.1, and Q1 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br; and / or, The general formula for the lithium-containing transition metal phosphate materials of the second type of particles includes Li m2 Fe x2 Mn r2 P y2 O j2 Q2 q2 Wherein, 0.95≤m2≤1.15, x2>0, r2>0, 0.9≤x2+r2≤1, 0.95≤y2≤1, 3.5≤j2≤4, 0≤q2≤0.1, and Q2 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

26. The battery cell according to any one of claims 20 to 25, characterized in that, The general compositional formula of the third type of particle-containing lithium transition metal phosphate materials includes Li m3 Fe x3 Mn r3 P y3 O j3 Q1 q3 Wherein, 0.95≤m3≤1.15, x3>0, r3≥0, 0.9≤x3+r3≤1, 0.95≤y3≤1, 3.5≤j3≤4, 0≤q3≤0.1, and Q3 includes one or more of Al, Na, K, Mg, Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, Ti, B, S, Si, N, F, Cl, and Br.

27. The battery cell according to any one of claims 1 to 26, characterized in that, The compaction density of the positive electrode sheet is 2.25 g / cm³. 3 -2.75g / cm 3 .

28. The battery cell according to any one of claims 1 to 27, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes one or more of the following: natural graphite, modified graphite, artificial graphite, graphene, carbon nanotubes, carbon nanofibers, porous carbon, tin, antimony, germanium, lead, ferric oxide, vanadium pentoxide, tin dioxide, titanium dioxide, molybdenum trioxide, elemental phosphorus, lithium titanate, and lithium terephthalate.

29. The battery cell according to any one of claims 1 to 28, characterized in that, The OI value of the negative electrode film is 3-30, optionally 8-25, and further optionally 10-15.

30. The battery cell according to any one of claims 1 to 29, characterized in that, The porosity of the negative electrode film is 20%-60%, and can be selected as 35%-45%.

31. The battery cell according to any one of claims 1 to 30, characterized in that, The areal density of the negative electrode film is 0.1 g / 1540.25 mm. 2 -0.2g / 1540.25mm 2 Available in 0.14g / 1540.25mm. 2 -0.19g / 1540.25mm 2 .

32. A battery device, characterized in that, The battery device includes the battery cell of any one of claims 1 to 31, and the battery device includes at least one of battery module, battery pack, and energy storage battery.

33. An electrical appliance, characterized in that, Includes the battery device as described in claim 32, wherein the battery device is used to provide electrical energy.

34. An energy storage device, characterized in that, Includes the battery device as described in claim 32, wherein the battery device is used to store electrical energy.

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